1. Field of the Invention
The present invention relates to vehicle braking systems and more particularly to improvements in drum brakes of a non-servo floating shoe.
2. Description of the Related Art
Drum brakes are well known and generally include a hollow cylindrical drum fixed to and rotatable with a vehicle wheel about a wheel axle axis and a non-rotating backing plate fixed to the vehicle supporting a hydraulic actuation device constituting the main brake motor. The hydraulic actuation device normally includes a wheel cylinder having two pistons that slide in a bore and defining between them a sealed chamber in which a rise in pressure causes separation of the pistons forcing the brake shoes into contact with the drum to attenuate rotation thereof. A drum brake may also include a mechanical actuation device to provide parking brake or emergency brake functions. First and second brake shoes are movably mounted on the backing plate each having a web and a rim with the rims having opposite the drum inner surface faces bearing friction linings. The hydraulic actuation device acts on a first end of the web of each shoe to press the friction linings against the drum. In some drum brake implementations, the brake shoes are pivotably attached to the backing plate or otherwise mechanically articulated. In floating shoe implementations, the shoes are be slidably mounted on the backing plate and a bearing component secured to the backing plate acts as a bearing surface for second ends of the webs of each shoe.
The bearing component may take the form of a block or anchor fixed to a raised portion of the backing plate, for example, by rivets. In the literature such backing plates are also referred to as carrier or support plates. Typically, there is a retainer extending laterally beyond the block to prevent axial movement of the shoe web away from the block. The retainer is normally fixed to the block by the same rivets which join the block to the support plate. Typical floating shoe drum brakes are shown, for example, in U.S. Pat. Nos. 5,360,086; 5,553,691; and 5,630,486. It is desirable to reduce the cost of producing a floating shoe drum brake.